Despite international criticism by human-rights groups of what they called Manning's "inappropriate" treatment at the Marine Corps base in Quantico, Va., the Pentagon said that the move "should not be interpreted as a criticism of the place he was before." Manning's defense counsel has said that he has been kept in solitary confinement and was stripped of his clothing.

Manning, 23, is suspected of leaking thousands of classified military documents relating to the wars in Afghanistan and Iraq to WikiLeaks -- and most recently, of leaking a quarter-million State Department documents. Manning was dealt 22 new charges in March, including the traditional capital offense of "aiding the enemy," after what the Army said was a seven-month investigation. Even so, the Army said at the time that it didn't intend to seek the death penalty.

The charges include wrongfully causing intelligence to be published on the Internet where it could be accessed by "the enemy," theft of public records, transmitting defense information, and fraud in connection with computers.

At Fort Leavenworth, the military's only maximum-security prison, Manning will likely be confined under less restrictive conditions than in Quantico. "When we have finished assessing his risk, he will be housed with the other pre-trial inmates," said Army Lt. Col. Dawn Hilton. "And a typical day is three square meals a day in a dining facility that the post-trials eat at. He'll receive open recreational time for three hours during the day, both indoors and outdoors. And he'll have the capability to interact with other pre-trial inmates on a routine basis."